This invention relates to the art of producing thin-walled honeycomb structures, such as those that would have utility as a substrate in emissions control from an internal combustion engine. Such substrates may be formed from extrudable material such as particulate ceramic and/or metal batches and similar materials which have the property of being able to flow or plastically deform during extrusion, while being able to become sufficiently rigid immediately thereafter so as to maintain their structural integrity, in the manner set forth in U.S. Pat. Nos. 3,790,654 and 4,758,272. Alternatively, the honeycomb structure may be made of pleated thin porous sheets of filter material whose layers are interleaved with corrugated or crimped spacers with the parallel corrugations or crimps thereof extending substantially perpendicular to the folds of the pleated sheets, as disclosed in U.S. Pat. Nos. 2,884,091, 2,952,333 and 3,242,649.
The invention particularly relates to the problem of abrasive edges surrounding the opposed faces at the longitudinal ends of metal honeycomb structures. That is, the opposed edges of such metal honeycomb structures each function as an unwanted cutting edge, and are a source of abrasion to insulating material which is utilized to surround the substrate and support it within and insulate it from an enclosing canister. The abrasive problem is further accentuated when attempting to round the edges, since such rounding only exposes more web surfaces and increases the amount of cutting or abrasion experienced by the surrounding insulating material.
It thus has been an object of the invention to provide a honeycomb structure having a rounded edge portion which does not detrimentally cut or abrade surrounding material.